通过重载CEdit类的onchar()函数，实现文本框的限制输入，可根据的自己的需求写限制条件-By overloading CEdit class onchar () function to achieve a text box to limit the importation, according to the needs of their own to write constraints

在控件上实现输入限制是经常用到的功能，本例主要介绍如何使文本框具有输入限制功能-In the control input constraints are frequently used functions, in this case mainly introduced how to make the text box with input constraint function